Uncommon salmonella traced back to raw ahi

State health investigators have identified a relatively rare type of salmonella poisoning on Oahu that they linked to similar cases on the mainland through "fingerprints" of the bacteria's DNA.

The illnesses are believed due to raw ahi imported and distributed to Hawaii and other places, said Dr. Paul Effler, state epidemiologist.

The state Department of Health believes the tuna had been previously frozen
and was then eaten raw.

The Food and Drug Administration is conducting a "traceback investigation," talking to distributors and to those affected about where they ate or bought the fish to try to determine if there is a common source, he said.

In Hawaii, Effler said, it looks as though people became ill after eating raw ahi mostly in poke but also sashimi. A sushi restaurant was involved in some mainland cases, he said.

About 30 cases have been confirmed on Oahu since October, said Janice Okubo, state Health Department spokeswoman. Five people were hospitalized but have been released, she said. "They have all recovered or are recovering."

The unusual culprit is known as salmonella Paratyphi B. Because it is rare "doesn't necessarily mean it's serious," Effler said. "It's just more uncommon."

Most illnesses involve diarrhea, fevers and chills, he said. "Most infections resolve on their own without need for antibiotics."

Hawaii has about 300 cases of salmonella food poisoning from various strains every year, Okubo said. There were 330 last year and 265 in 2006. Usually, only about 10 cases of Paratyphi B occur annually, she said.

Scattered cases began occurring in October in different parts of Oahu, she said.

"Nothing was exactly the same with these cases, and because in Hawaii there is so much consumption of fish and so much fish is brought in, it was difficult to knock down," she added.

The Health Department launched in November "what ultimately was a fairly intensive investigation," Effler said. A study was done of all cases, asking people who became ill what they ate the week before. They were matched by age to people in the neighborhood, with three people interviewed for each case about what they ate during the same week, he said.

Health researchers drew a "geographic border" around the addresses of those affected, got phone numbers and called people of the same age in the area, asking if they were sick and what they ate for the week involved, he said.

"It's an imperfect tool, but when we get enough people responding, it's amazing how often we can get the difference between people who got sick and those who didn't," Effler said. "Fortunately, people in Hawaii are willing to talk to us, and we were able to get enough control people to respond to statistically implicate raw fish/ahi consumption."

In the last few weeks, Effler said, his office became aware of some cases on the mainland, so they fingerprinted the germ's DNA through a national database.

"Lo and behold, two cases in Colorado ultimately matched by the DNA fingerprint had consumed raw fish the week before the illness," he said. "Also, a case in California had fish exposure. This pretty much convinced us the source was likely to be raw fish brought in and distributed not just to Hawaii."